Abstract
Travertine and nontravertine thermal springs have been studied in Yunlong County in southwest China to determine the geothermal reservoir temperatures and to find the geochemical processes that affect the evolution of thermal groundwater constituents during subsurface circulation. Hydrochemical characteristics distinguish travertine from nontravertine types. Travertine springs show HCO3·Cl-Na and SO4·HCO3-Ca·Na type, and a nontravertine spring presents Cl·HCO3·SO4-Na type. Log(Q/K) versus T diagrams show that reservoir temperatures can be expressed as intervals based on the equilibrium mineral assemblages coexisting in equilibrium and multiminerals in equilibrium with the aid of the PHREEQC and WATCH programs. The spring water mixing ratio with shallow water is between 59% and 82% with steam loss ranging from 12.1% to 27.8%. The Dalang Spring mixes with the highest proportion of cold water (76% to 82%) among the four hot springs and has the highest geothermal reservoir temperature (132°C to 176.9°C). The water-rock interaction during recharge from precipitation demonstrates that the minerals halite, kaolinite, chalcedony, plagioclase, and CO2(g) play an important part in the evolution of the thermal groundwater. Four inverse modeling simulation paths between precipitation and spring discharge were established to calculate the mass flux of minerals by the PHREEQC program. Halite, kaolinite, chalcedony, plagioclase, and CO2(g) participate in dissolution reactions in the thermal groundwater circulation, while gypsum, calcite, dolomite, biotite, and fluorite keep the geochemical processes in equilibrium.
Highlights
The hydrogeochemistry, geothermometry, and quantification of fluid-mineral reactions from four hot springs along the Bijiang River in Yunlong County of the Lanping basin in southwest China have been examined with respect to the major element compositions of the reservoir fluid discharging on the land surface
Shi et al [2] studied the hydrochemical characteristics of thermal groundwater in the eastern Tibetan Plateau geothermal belt and found that the springs originated from snow melt in the mountains and surface water and that the groundwater was dominated by the hydrochemical interactions with host rocks
Based on the geochemical data obtained from four hot springs along the Bijiang River, this study presents the distinctive hydrochemical characteristics, establishes the mineral equilibrium status, identifies the mixing behavior of geothermal fluids, and simulates the circulation of hot spring thermal groundwater
Summary
The hydrogeochemistry, geothermometry, and quantification of fluid-mineral reactions from four hot springs along the Bijiang River in Yunlong County of the Lanping basin in southwest China have been examined with respect to the major element compositions of the reservoir fluid discharging on the land surface. In the complex circulation processes, water-rock interactions play an important part in hydrogeochemical indicators of the waters in the geothermal systems which can be used to examine the properties of geothermal reservoirs and the mixing behavior of groundwater [1,2,3,4]. Geothermometrical methods use mineral solubilities as a function of temperature and silica-enthalpy of liquid water in equilibrium with steam to indicate the reservoir temperature under certain circumstances with respect to the chemical characteristics of thermal groundwater during an ascent from an aquifer to the surface [5,6,7,8,9,10]. Based on the geochemical data obtained from four hot springs along the Bijiang River, this study presents the distinctive hydrochemical characteristics, establishes the mineral equilibrium status, identifies the mixing behavior of geothermal fluids, and simulates the circulation of hot spring thermal groundwater
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